Need a battery tester right away?

[ebow86]

If a person is new to rechargables and they spent their entire budget on a high quality charger (PILA IBC) and cells (protected AW 17500) and didn't have the money right away to get a decent battery tester, would they be ok for a little while if they took care with the batteries? Or is a battery tester completely essential right away?

 

[Quension]

A tester isn't required.

What you should get ASAP is a DMM -- even a cheap one is fine (people seem to like ones from Harbor Freight, for instance). If you can borrow one, that's fine too. This will let you check State of Charge on your 17500s, which is always useful, and serves as a sanity check when things act strange.

To check the accuracy of your DMM, just compare it with something you know -- e.g. a brand new alkaline should be about 1.6V.

 

[Burgess]

I think you will find a Brand New Alkaline to show 1.6 volts.


_

 

[StarHalo]

$3 for a digital multimeter, this one also features a load tester to test regular batteries.

 

[Quension]

I think you will find a Brand New Alkaline to show 1.6 volts.

Fixed post.

I suppose that's a lousy example anyway -- chances are you have a power supply or several somewhere (wall wart / adapter) with specs on it. Just check the output of a couple of those.

 

[TakeTheActive]

$3 for a digital multimeter, this one also features a load tester to test regular batteries.

One setting, ~370 ohms, for both 1.5V and 9V:

• ~4mA LOAD @ 1.5VDC :thumbsdow
• ~25mA LOAD @ 9VDC :thumbsup:

I prefer the ~150mA for AA/C/D and ~50mA for AAA/N from my 'ancient' RadioShack 22-090 Battery Tester when either both of my SMART Charger / Analyzers are in use or I'm checking one of my *CRAP* (High Internal Resistance) cells.

I also ordered the analog version of the 'caliper-style' Chinese tester referred to here within a month or so ($0.99 COUPON *SALE* @ Meritline - how could I resist? ) just to take it apart and see what they used for a LOAD (while I wait for the digital version to also, eventually, go on *SALE* ).

 

[syncytial]

Fixed post.

I suppose that's a lousy example anyway -- chances are you have a power supply or several somewhere (wall wart / adapter) with specs on it. Just check the output of a couple of those.

Unfortunately, many wall warts are unregulated, and even the regulated ones are rarely close enough to their nominal voltage to be useful as a voltage reference. It's fairly typical for a "9V" wall wart to be up to 12V unloaded.

When we're concerned about +/- 5 mV, you need a reference with accuracy that exceeds that to be useful.

I'll measure a few wall warts for examples.



- Syncytial.

 

[TakeTheActive]

...chances are you have a power supply or several somewhere (wall wart / adapter) with specs on it. Just check the output of a couple of those.

And on most, the output will VARY greatly depending upon the LOAD it's feeding.

How about the +5VDC buss on a PC? :thinking:

Sacrifice a USB cable, solder a red and black INSULATED mini alligator clip on VCC and GND respectively, and see what you get when the PC is idling.

 

[syncytial]

OK, here are some wall wart measurements...

All are unloaded. The non-regulated ones also drifted a few hundred millivolts while testing, so I won't report excessive sig figs.

These measurements were made with a Fluke 87-V, in hi-res mode.

Device                         measured       nominal

IBM laptop supply             16.600            16
Dell laptop supply            19.640            19.5
Asus netbook supply           12.232            12
Pila IBC supply #1            6.225              6
Pila IBC supply #2            6.229              6
Maha C9000 supply             12.320            12
HID supply #1                 22.9               15
HID supply #2                 23.0               15
HID supply #3                 23.2               15
LiIon Charger                 4.695              4.6
12V supply (A)                19.3               12
12V supply (B)                16.2               12
12V supply (C)                20.1               12

The three HID supplies are identical - two with identical manufacturing dates, and one from a year later.

The three "12V" supplies are generic units supplied with different gear, and are each different from the others.

So, unless you have a known, stable voltage reference or meter, you can't just assume that something that is marked as X volts will provide exactly X volts. The measured values will vary under varying loads as well. How well regulated a supply is will determine how much it varies.

Inexpensive power supplies will typically have measurable AC ripple, hum and possibly high frequency components (if a switching supply) which could affect an inexpensive meter's reading too.

I wouldn't trust even a 5V computer power supply to be within 5 mV without verification and confirmation of it's stability.


- Syncytial.

 

[Quension]

When we're concerned about +/- 5 mV, you need a reference with accuracy that exceeds that to be useful.

No -- what I was going for was +/- 100mV or so. Any more accuracy is not required for basic checks when you have equipment that already works and you can take measurements as a baseline. All the OP needs to do is take measurements of the what he has while it's working, and note the results. The differences are what's important when something strange happens.

This was meant as an approximate check that a random DMM is working, not a reference-quality calibration. I didn't explain that, which was misleading -- sorry about that :fail:

I'll concede the point of wild wall warts -- that is why I said to check more than one, but I assumed too much about the average. I was also thinking of low-voltage low-power supplies at the time, which tend to be more stable unloaded. Still a bad call though, especially given the Pila supply would have been a logical choice for the OP to look at

I'll leave the recommendations to you guys.

 

[TakeTheActive]

...These measurements were made with a Fluke 87-V, in hi-res mode...

---SNIP---

...So, unless you have a known, stable voltage reference or meter, you can't just assume that something that is marked as X volts will provide exactly X volts. The measured values will vary under varying loads as well. How well regulated a supply is will determine how much it varies...

I agree. This is basically the same information that I posted.

...I wouldn't trust even a 5V computer power supply to be within 5 mV without verification and confirmation of it's stability...

I agree with this also, *BUT*, IMHO, a +5VDC PC buss, at idle, should be *MUCH* CLOSER to its rated voltage than a random wallwart or adapter.

[OPINION]

• IDEALLY, the OP (let's assume a 'Loner', with no local 'Technical' buddies , trying to spend the LEAST amount of money as possible), would buy a 'Voltage Reference' (for ~$20 on eBay, IIRC), look inside his 'el-cheapo' DMM for a glyptalled pot (potentiometer - variable resistor), adjust the 'el-cheapo' DMM's reading to match the 'Voltage Reference', dab on some nail polish and be set. TOTAL INVESTMENT: ~$22 (with the Harbor Freight DMM on *SALE*).
  Alternatively, s/he would note the DIFFERENCE and place a label with the difference / 'Correction Factor' on the 'el-cheapo' DMM.
  .
• *IF* the OP *HAS* some local 'Technical' buddies, with 'more expensive / accurate' DMMs, I feel that the reading from the +5VDC buss on a SPECIFIC, idle PC should be fairly repeatable. Thus, for example, taking the reading with a Fluke and then 'tweaking' the 'el-cheapo' DMM to match, should be 'close enuf' for someone on a tight budget.
  (Otherwise, just buy a Fluke!)
  .
• New alkalines, wallwarts, adapters, etc..., IMHO, will be inconsistent as 'Voltage References'.

[/OPINION]

Bottom Line: The OP is looking for the MOST INEXPENSIVE, but STILL ACCURATE METHOD, to monitor the charge state of his new protected AW 17500 cells.

Best to worst (mentioned so far):

• Fluke (or other high quality) DMM.
• 'Other' DMM, with difference from 'Voltage Reference' either adjusted out or noted on label.
• 'Other' DMM, with difference from '+5VDC PC buss reading on Fluke, or equivalent, DMM' either adjusted out or noted.

 

[syncytial]

No -- what I was going for was +/- 100mV or so. Any more accuracy is not required for basic checks when you have equipment that already works and you can take measurements as a baseline. All the OP needs to do is take measurements of the what he has while it's working, and note the results. The differences are what's important when something strange happens.

That's a reasonable strategy when the initial state is known, or highly likely to be, good - look for deviation from the norm and investigate should it arise.

Given the OP's question about the requirement for a battery tester when using a Pila charger and AW cells, I agree that it's not a requirement to have lab grade testing equipment in order to monitor for undesirable changes, especially since both Pila and AW products have earned the respect they have.

I'd still prefer to establish the baseline for correct operation of the charger with a more accurate meter, but I'll concede it's not really necessary.

As for my reference to +/- 5mV... If you're simply aiming to get an idea of state of charge of a battery, then +/- 100mV is fine. I was also considering the question of correct (safe) termination voltage when charging LiIon cells, which apparently requires tighter tolerances.

I'm fundamentally in agreement with TTA. (BTW, when I checked yesterday, there weren't any of the inexpensive voltage references available on the 'Bay, though there likely will be again).

It's not necessary to buy a Fluke to check batteries (and a Fluke isn't going to be automatically and permanently absolutely correct). Many less expensive meters will be stable and accurate enough, especially if they can be verified against a known-good reference of the required accuracy.


- Syncytial.